Automatic aquarium heater



FIG. 1 is a front elevation view of an automatic aquarium heater, showing my new design, the rear being substantially a mirror image of that shown except for the absence of the numbers and the mercury bulb;

FIG. 2 is a side elevation view thereof;

FIG. 3 is a top plan view thereof; and

FIG. 4 is a bottom plan view thereof. 

The ornamental design for an automatic aquarium heater, as shown and described. 